Work vehicles, including, but not limited to, agricultural work vehicles such as tractors and combines, as well as construction vehicles, such as loaders and backhoes, are often supported by a set of inflatable tires. The inflation pressure of these inflatable tires can be adjusted to provide a substantially cushioned ride while providing adequate traction support for the vehicle. Maintaining proper tire inflation provides better maneuverability and control of the work vehicle while minimizing the amount of vehicle slip, thereby increasing the amount of traction and power available for the vehicle. Further, maintaining proper tire inflation reduces the amount of fuel necessary during operation of the work vehicle and provides improved tire wear, thereby providing substantial cost savings. A number of factors and conditions exist which cause work vehicles to be operated despite having a non-optimal or improper tire inflation pressure. For example, tire inflation pressure is typically decreased gradually over time to a low-level by leaks and imperfect seals, and typically tire inflation pressure fluctuates as a function of temperature. In addition, the optimal tire inflation pressure will vary based upon the operating conditions of the work vehicle, such as the vehicle speed, the type of terrain, and the mission. In addition, the optimal tire inflation pressure depends upon the operating loads placed on the tires under various operating conditions, and possibly the slip of the vehicle tires.
It is well known that pneumatic tires are best operated at specific inflation pressures to optimize tire and vehicle performance for combinations of speed, load, terrain, and mission. Tire inflation pressure directly affects the tire shape, deflection, tire contact patch shape, tire contact patch area, resonant frequency, hysteresis, and other characteristics. Pneumatic tires are the power transmitting element and the whole or partial suspension in wheeled vehicles. Tire inflation pressures influence many vehicle parameters, including, but not limited to, load capacity, tractive ability, ride, handling, braking, stability, mobility, speed, rolling resistance, soft soil performance, and obstacle negotiation. It is advantageous to tailor the tire inflation pressure to match the vehicle operating environment and duty cycle. This is particularly true for on/off highway and off highway vehicles such as agricultural tractors and construction equipment operating over improved and unimproved terrain surfaces at multiple speeds and vehicle loads.
Well-known central tire inflation methods exist to generate, control, and distribute compressed air to vehicle tires. To enable these functions, all centrally supplied tire inflation systems require a means to deliver air from a source of pressurized air on the fixed chassis through a rotary seal to the rotating wheel and tire. Agricultural tractors and construction equipment are often equipped with a bar axle or like axle arrangement where the axle shaft extends from the axle housing supporting a hub that translates along the axle shaft length or is fixed to the distal end. The axle shaft is a primary load supporting and torque transmitting member. Bearings supporting the axle shaft are typically located in the axle housing fixed to the differential housing. Axles are equipped with single or multiple tire sets sometimes requiring a separate tire inflation pressure for an individual tire or tire set.
To operate a central tire inflation system, it is necessary to provide pressurized air to and from the inflatable wheels while the wheels are rotating. To maintain an air supply to and from the rotating inflatable wheels, the wheel assembly must include a seal arrangement that allows the wheel to rotate while keeping pressurized air within the inflatable wheels. The seal arrangement must allow for selectively inflating and deflating the wheel as the wheel rotates.
Well-known methods exist for delivering air or a vacuum to a rotating wheel through a rotary joint or seal located in a hub, or a planetary hub assembly. However, known methods do not include delivering compressed air or vacuum to a bar axle with adjustable track width or similar axle shaft arrangements with single and multiple tire sets.
One method for delivering air or a vacuum to a rotating wheel (as used in Rockwell, EATON, Oshkosh, and other axle applications) locates air passages in a fixed skein, spindle, or through or under a sleeve placed over the skein concentric to the wheel bearings, into air seals located between the wheel bearings in the rotating hub and through passages in the hub to fittings leading to the wheel and tire. This method, however, does not include transferring compressed air or a vacuum to a wheel where the wheel hub is not fixed along the axle shaft length or a wheel carrying hub where the wheel bearings are not included in the hub assembly.
Another method for delivering air or a vacuum to a rotating wheel (as used in AM General and other axle applications) conducts air through a passage formed inside a skein or non-rotating axle shaft, with the air passing through the solid shaft or skein to a rotary air fitting fitted at the distal end and connected through a conduit to the wheel valve. This method is useful for non-driving axles, particularly non-driving steering axles or non-center drive axles such as a portal axle.
Still another method for delivering air or a vacuum to a rotating wheel (as used in KMAZ and other axle applications) conducts air through a passage formed inside the drive shaft with a rotating seal located inside the axle housing. Compressed air passes through the rotary seal into the axle shaft to the rotating hub where passages or flexible conduits conduct air to the wheel assembly. This method requires a port passing through the drive shaft length, and does not provide for a hub that translates along the axle length.
Still another method for delivering air or a vacuum to a rotating wheel (as used in Possges and Tigges and other axle applications) delivers air to the rotating wheel entirely through a conduit passing outside the tire from the fixed vehicle chassis to a rotary seal mounted to the axle shaft distal end. A second conduit transfers air from the rotary seal to the wheel tire assembly along the axle shaft. This method is applicable to bar axles and the like, but requires a hose passing outside the vehicle and tire, the hose being subject to entanglement.
Still another method for delivering air or a vacuum to a rotating wheel (as used in Timken Bearing Corporation applications) employs a wheel bearing race containing ports or channels to pass air between the wheel bearings with air seals located outside the wheel bearing. The method does not include transferring compressed air or a vacuum to a wheel where the wheel hub is not fixed along the axle's length or a wheel carrying hub where the wheel bearings are not included in the hub assembly. The method also does not provide for oil bath lubrication.
Accordingly, it would be advantageous to provide a seal arrangement for a wheel hub that provides the ability to tailor tire inflation pressure to wheel load, vehicle speed, mission, terrain, and other parameters while stationary or underway.
Further, it would be advantageous to provide a seal arrangement that provides for the delivery of air to a wheel mounted to a bar axle or like arrangement that is easily retrofittable with little or no modification.
Still further, it would be advantageous to provide an apparatus for transmitting air to a wheel assembly mounted to a bar axle or like axle that does not interfere with the ability to change the vehicle track width.
Still further, it would be advantageous to provide a seal arrangement for transmitting air to a wheel assembly mounted to a bar axle or like axle that uses a conventional wheel and tire.
Still further, it would be advantageous to provide an apparatus for transmitting air to a wheel assembly mounted to a bar axle or like axle that optionally permits independently controlled inflation pressure to individual tires or tire sets.
Still further, it would be advantageous to provide an apparatus for transmitting air to a wheel assembly mounted to a bar axle or like axle that is installed as a separate unit fixed to the axle housing.